The present invention relates to a fuel injection system for an externally ignited internal combustion engine.
The system according to the present invention operates on fuel which is continuously injected into the suction tube of the engine in which an air sensing element and an arbitrarily operable throttle valve (butterfly valve) are disposed in series. The sensing element is displaced by and in proportion to the throughgoing quantity of air against a restoring force. In the course of its excursion the sensing element displaces a movable component of a valve which is disposed in the fuel supply line and which is intended for metering a quantity of fuel which is proportionate to the quantity of air. The aforenoted restoring force is supplied by liquid under pressure which is delivered continuously through a control pressure line which is separated from the fuel supply line by an uncoupling throttle and which exerts a force on a control plunger. The pressure of the pressurized liquid is variable by at least one electromagnetic valve controllable as a function of the operating parameters of the internal combustion engine and by at least one pressure regulating valve containing a temperature-dependent heatable control element.
Fuel injection systems of this type are designed to automatically provide an advantageous fuel-air mixture for all operational conditions of the internal combustion engine so as to burn the fuel as completely as possible and thus prevent toxic gases from being produced, or at least to considerably reduce the same while obtaining maximum performance of the internal combustion engine with minimum fuel consumption. The quantity of fuel must therefore be very accurately metered in accordance with the requirements of each operational state of the internal combustion engine and the air-fuel ratio must be varied as a function of the operating parameters such as speed, load, temperature and exhaust gas composition.
In the case of known fuel injection systems of this type, the quantity of fuel which is metered is, as far as possible, proportionate to the quantity of air flowing through the suction tube and this metered quantity of fuel may be varied by changing the restoring force of the sensing element as a function of the operating parameters by means of an electromagnetic valve.